basis of record Bouillon, J.; Boero, F. (2000). Synopsis of the families and genera of the Hydromedusae of the world, with a list of the worldwide species. Thalassia Salent. 24: 47-296 (look up in IMIS) [details]

basis of record(ofLimnopolypae) Costello, M.J.; Emblow, C.; White, R. (Ed.). (2001). European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification. Collection Patrimoines Naturels, 50. Muséum national d'Histoire Naturelle: Paris, France. ISBN 2-85653-538-0. 463 pp. (look up in IMIS) [details]

Diagnosis Hydroid small, simple, mostly solitary, some forming colonies; sessile; with or without tentacles; without theca but having a mucoprotein periderm, cysts and stolons can be covered by perisarc.
Medusa mostly with 4 complete radial canals, 6 also possible, often also with incomplete centripetal canals not reaching manubrium; with or without marginal nematocyst ring; gonads along radial canals or exceptionally on manubrium (Armorhydra and Limnocnida); marginal tentacles peripheral, hollow, without true basal bulb, marginal sense organs as internal enclosed statocysts of endo-ectodermal origin, embedded in the mesogloea near ring canal or in the velum; no ocelli; exceptionally reduced medusoids (Monobrachium).
Some species also in freshwater.[details]